Monomers for photovoltaic applications

ABSTRACT

A method of combining different materials to produce the comonomerwherein X1 and X2 are independently selected from the group consisting of: F, Cl, H, and combinations thereof and wherein R1 is independently selected from unsubstituted or substituted branched alkyls with 1 to 60 carbon atoms and unsubstituted or substituted linear alkyls with 1 to 60 carbon atoms.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims thebenefit of and priority to U.S. Provisional Application Ser. No.63/178,600 filed Apr. 23, 2021, entitled “Monomers for PhotovoltaicApplications,” which is hereby incorporated by reference in itsentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

This invention relates to polymers for organic photovoltaics.

BACKGROUND OF THE INVENTION

Solar energy using photovoltaics requires active semiconductingmaterials to convert light into electricity. Currently, solar cellsbased on silicon are the dominating technology due to their high powerconversion efficiency. Recently, solar cells based on organic materialsshowed interesting features, especially on the potential of low cost inmaterials and processing.

Organic photovoltaic cells have many potential advantages when comparedto traditional silicon-based devices. Organic photovoltaic cells arelight weight, economical in the materials used, and can be deposited onlow cost substrates, such as flexible plastic foils. However, organicphotovoltaic devices typically have relatively low power conversionefficiency (the ratio of incident photons to energy generated) and poorfilm forming ability.

There exists a need for a polymer to create organic photovoltaic cellsthat has high solution extinction coefficients, superior film formingability and high photovoltaic performance.

BRIEF SUMMARY OF THE DISCLOSURE

A method of combining

tris(dibenzylideneacetone)dipalladium(0), and tris(o-tolyl)phosphine toproduce

is then combined with n-bromosuccinimide and anhydrous tetrahydrofuranto produce the comonomer

In this comonomer, X₁ and X₂ are independently selected from the groupconsisting of: F, Cl, H, and combinations thereof and R₁ isindependently selected from unsubstituted or substituted branched alkylswith 1 to 60 carbon atoms and unsubstituted or substituted linear alkylswith 1 to 60 carbon atoms.

In an alternate embodiment, a method is taught for combining

tris(dibenzylideneacetone)dipalladium(0), and tris(o-tolyl)phosphine toproduce

is then combined with n-bromosuccinimide and anhydrous tetrahydrofuranto produce the comonomer

In this comonomer, X₁ and X₂ are independently selected from the groupconsisting of: F, Cl, H, and combinations thereof and R₁ isindependently selected from unsubstituted or substituted branched alkylswith 1 to 60 carbon atoms and unsubstituted or substituted linear alkylswith 1 to 60 carbon atoms.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefitsthereof may be acquired by referring to the follow description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a conventional device architecture and an inverted devicearchitecture.

FIG. 2 depicts the H NMR of a compound.

FIG. 3 depicts the H NMR of a compound.

FIG. 4 depicts the H NMR of a compound.

FIG. 5 depicts the H NMR of a compound.

FIG. 6 depicts the F NMR of a compound.

FIG. 7 depicts the H NMR of a compound.

FIG. 8 depicts the H NMR of a compound.

FIG. 9 depicts the H NMR of a compound.

FIG. 10 depicts the H NMR of a compound.

FIG. 11 depicts the F NMR of a compound.

FIG. 12 depicts the current density over voltage for the Polymer A.

DETAILED DESCRIPTION

Turning now to the detailed description of the preferred arrangement orarrangements of the present invention, it should be understood that theinventive features and concepts may be manifested in other arrangementsand that the scope of the invention is not limited to the embodimentsdescribed or illustrated. The scope of the invention is intended only tobe limited by the scope of the claims that follow.

“Alkyl,” as used herein, refers to an aliphatic hydrocarbon chains. Inone embodiment the aliphatic hydrocarbon chains are of 1 to about 100carbon atoms, preferably 1 to 30 carbon atoms, and includes straight andbranched chained, single, double and triple bonded carbons such asmethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,t-butyl, n-pentyl, isopentyl, neo-pentyl, n-hexyl, isohexyl, thenyl,propenyl, butenyl, pentenyl, hexenyl, butadienyl, pentadienyl,hexadienyl, ethynyl, propynyl, butynyl, pentynyl, hexynyl, 2-ethylhexyl,2-butyloctyl, 2-hexyldecyl, 2-octyldedodecyl, 2-decyltetradecy and thelike. In this application alkyl groups can include the possibility ofsubstituted and unsubstituted alkyl groups. Substituted alkyl groups caninclude one or more halogen substituents.

“Alkoxy,” as used herein, refers to the group R—O— where R is an alkylgroup of 1 to 100 carbon atoms. In this application alkoxy groups caninclude the possibility of substituted and unsubstituted alkoxy groups.

“Aryl” as used herein, refers to an optionally substituted, mono-, di-,tri-, or other multicyclic aromatic ring system having from about 3 toabout 50 carbon atoms (and all combinations and subcombinations ofranges and specific numbers of carbon atoms therein), with from about 6to about 20 carbons being preferred. Non-limiting examples include, forexample, phenyl, naphthyl, anthracenyl, and phenanthrenyl. Aryl groupscan be optionally substituted with one or with one or more Rx. In thisapplication aryl groups can include the possibility of substituted arylgroups, bridged aryl groups and fused aryl groups. As used herein arylgroups also include heteroaryls, including structures with more than oneheteroatom. Non-limiting examples of heteroatoms that can be heteroarylsinclude B, N, O, Al, Si, P, S, Ge, Bi, Te, Sn, and Se. Some non-limitingexamples of aryl groups with heteroaryls include: thiophene, pyridine,pyrrole, furan, stibole, arsole selenophene, imidazole, pyrazole,oxathiole, isoxathiole, thiazole, triazole, thiadiazole, diazine,oxazine, indole, and thiazine.

“Ester”, as used herein, represents a group of formula —COOR wherein Rrepresents an “alkyl”, “aryl”, a “heterocycloalkyl” or “heteroaryl”moiety, or the same substituted as defined above

“Ketone” as used herein, represents an organic compound having acarbonyl group linked to a carbon atom such as —C(O)Rx wherein Rx can bealkyl, aryl, cycloalkyl, cycloalkenyl or heterocycle.

“Amide” as used herein, represents a group of formula“—C(O)NR^(x)R^(y),” wherein R^(x) and R^(y) can be the same orindependently H, alkyl, aryl, cycloalkyl, cycloalkenyl or heterocycle.

The following examples of certain embodiments of the invention aregiven. Each example is provided by way of explanation of the invention,one of many embodiments of the invention, and the following examplesshould not be read to limit, or define, the scope of the invention.

Device Architecture

When used as a photovoltaic device the architecture may be aconventional architecture device, while in others it may be an invertedarchitecture device. A conventional architecture device typicallycomprised of multilayered structure with a transparent anode as asubstrate to collect positive charge (holes) and a cathode to collectnegative charge (electrons), and a photo-active layer sandwiched inbetween two electrodes. An additional charge transport interlayer isinserted in between active layer and electrode for facile hole andelectron transport. Each charge transport layer can be consisted of oneor more layers. An inverted device has the same multilayered structureas the conventional architecture device whereas it uses a transparentcathode as a substrate to collect electrons and an anode to collectholes. The inverted device also has the photo-active layer andadditional charge transport layers sandwiched in between two electrodes.FIG. 1 depicts a conventional device architecture and an inverted devicearchitecture.

Polymer

In one embodiment the polymer can comprise

wherein m+n=1.

In this embodiment, R′, R″, R′″, and R″″ can be independently selectedfrom an alkyl group, an aryl group, an alkoxy group, a thioalkoxy group,or combinations thereof. In another embodiment, R′, R″, R′″, and R″″ areindependently selected from the group selected from:

or combinations thereof, wherein R₉, R₁₀, R₁₁, R₁₂, R₁₃, and R₁₄ areindependently selected from F, Cl, H, an alkyl group, an aryl group, analkoxy group, a thioalkoxy group, or combinations thereof.

In another embodiment the polymer can comprise:

wherein m+n=1

In one embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ are independentlyselected from substituted, unsubstituted, straight-chain, branched, orcyclic alkyls ranging from 1 to 100 carbon atoms. In another embodiment,they can be selected from 1 to 60 carbon atoms. In yet anotherembodiment, R₁, R₂, R₅, and R₆, can be identical; or R₃, and R₄, areidentical; or even R₇, and R₈, are identical.

In one non-limiting example alkyl groups can include 2-ethyl-hexyl,2-butyl-octyl, 2-hexyl-decyl, and 2-octyl-dodecyl.

In one embodiment, R₁₅, R₁₆, R₁₇, and R₁₈ can be independently selectedfrom H, Cl, or F. In some embodiments, R₁₅ and R₁₆ can be the same asR₁₇ and R₁₈. In other embodiments R₁₅ and R₁₆ are different than R₁₇ andR₁₈.

In yet another embodiment, X₁, X₂, X₃, and X₄ are independently selectedfrom the group consisting of: F, Cl, H, and combinations thereof.

In yet another feature of this embodiment, the number of monomer repeatunits in the polymer can range from about 1 to about 100,000 repeatunits. In other features of this embodiment, the number of monomerrepeat units in this polymer can range from about 10 to about 75,000repeat units, about 100 to about 50,000 repeat units or even from about1,000 to about 20,000 repeat units. Additionally, in this polymer n+m =1or alternatively, m=0.3 to 0.5 and n=0.5 to 0.7 or even, m=0.4 andn=0.6.

It is also envisioned that this polymer can be regio-regular orregio-random. It is also envisioned that the polymer can be used as aphotovoltaic material or as an active layer in an electronic device.

In yet another embodiment, the polymer can comprise:

Monomer Synthesis

A method of combining

tris(dibenzylideneacetone)dipalladium(0), and tris(o-tolyl)phosphine toproduce

This is then followed by combining

with n-bromosuccinimide and anhydrous tetrahydrofuran to produce thecomonomer

In this method X₁ and X₂ are independently selected from the groupconsisting of: F, Cl, H, and combinations thereof, and R₁ isindependently selected from unsubstituted branched alkyls with 1 to 60carbon atoms. In some embodiments, X₁ and X₂ are independently selectedfrom the group consisting of: F, Cl, and H, wherein H can only be in X₁and X₂ but not in both.

Through this process different repeat units can be made such as

In these embodiments, X₁ and X₂ can be independently selected from thegroup consisting of: F, Cl, H, and combinations thereof. R′ and R″ canbe independently selected from an alkyl group, an aryl group, orcombinations thereof. In other embodiments, R′ and R″ can beindependently selected from the group selected from:

or combinations thereof, wherein R9, R10, R11, R12, R13, and R14 areindependently selected from F, Cl, H, an alkyl group, an aryl group, orcombinations thereof. Additionally, R₁, R₂, R₃, and R₄ can beindependently selected from unsubstituted branched alkyls with 1 to 60carbon atoms and unsubstituted linear alkyls with 1 to 60 carbon atoms.Additionally, R₁₅ and R₁₆ can be independently selected from H, F, Cland combinations thereof.

In another embodiment, the monomer synthesis can be combining

tris(dibenzylideneacetone)dipalladium(0), and tris(o-tolyl)phosphine toproduce

This is then followed by combining

with n-bromosuccinimide and anhydrous tetrahydrofuran to produce thecomonomer

In this method R₁ is independently selected from unsubstituted branchedalkyls with 1 to 60 carbon atoms.

In one embodiment, 2-bromo-3-(2-butyloctyl)thiophene,(3,3′-difluoro-[2,2′-bithiophene]-5,5′-diyl)bis(trimethylstannane),Pd2dba3, and P(o-tol)3 were combined. The mixture was degassed withargon twice before anhydrous toluene was added. The solution was thenheated. After removal of solvent, the crude product was purified bycolumn chromatography on silica gel using a mixture of dichloromethaneand hexane as eluent to produce the following compound

The 1H NMR spectrum of the compound is shown in FIG. 2, with theenlarged aromatic region provided in FIG. 3.

The synthesis then continues by taking compound3,3′″-bis(2-butyloctyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiopheneand adding anhydrous THF and N-bromosuccinimide. The reaction is thenstirred and stopped by adding saturated potassium carbonate solution.After the removal of solvent, the resulting mixture was subjected tocolumn purification to produce

The 1H NMR spectrum of the compound is shown in FIG. 4, with theenlarged aromatic region provided in FIG. 5. The F NMR spectrum isprovided in FIG. 6.

In another embodiment, 2-bromo-3-(2-hexyldecyl)thiophene,(3,3′-difluoro-[2,2′-bithiophene]-5,5′-diyl)bis(trimethylstannane),Pd2dba3, and P(o-tol)3 were combined. The mixture was degassed withargon twice before anhydrous toluene was added. The solution was thenheated. After removal of solvent, the crude product was purified bycolumn chromatography on silica gel using a mixture of dichloromethaneand hexane as eluent to produce the following compound

The 1H NMR spectrum of the compound is shown in FIG. 7, with theenlarged aromatic region provided in FIG. 8.

The synthesis then continues by taking compound3,3′″-bis(2-hexyldecyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiopheneand adding anhydrous THF and N-bromosuccinimide. The reaction is thenstirred and stopped by adding saturated potassium carbonate solution.After the removal of solvent, the resulting mixture was subjected tocolumn purification to produce

The 1H NMR spectrum of the compound is shown in FIG. 9, with theenlarged aromatic region provided in FIG. 10. The F NMR spectrum isprovided in FIG. 11.

Polymer Synthesis

The polymerization can be any conventionally known method of combiningthe monomers into a covalently bonded chain or network. In onenon-limiting example the monomers can be polymerized using Stille crosscoupling, Suzuki cross coupling or direct arylation polymerization.

In another embodiment, the polymerization can be performed by combining

tris(dibenzylideneacetone)dipalladium(0), tris(o-tolyl)phosphine, andanhydrous chlorobenzene to produce a solution. The solution is thenpurified and dried to produce

In this embodiment wherein n+m=1, and X1, X2, X3, and X4 areindependently selected from the group consisting of: F, Cl, H, andcombinations thereof. Additionally, in this embodiment, R1, R2, R3, R4,R5, R6, R7, and R8 are independently selected from unsubstitutedbranched alkyls with 1 to 60 carbon atoms. There are a variety ofdifferent permutations with this method such as X1 and X2 beingidentical; X3 and X4 being identical; R₁, R₂, R₅, and R₆ beingidentical; R₃ and R₄ being identical; and R₇ and R₈ being identical.

In yet another method involves combining

tris(dibenzylideneacetone)dipalladium(0), tris(o-tolyl)phosphine, andanhydrous chlorobenzene to produce a solution. The solution is thenpurified and dried to produce

In this embodiment wherein n+m=1, and R₁, R₂, and R₃ are independentlyselected from unsubstituted branched alkyls with 1 to 60 carbon atoms.

Polymer A Synthesis

In yet another embodiment, the polymer synthesis can be compounds5,5′″-dibromo-3,3′″-bis(2-butyloctyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiophene,5,5′″-dibromo-3,3′″-bis(2-hexyldecyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiophene,(4,8-bis(5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(trimethylstannane),Pd2dba3 and P(o-tol)3 were added. The mixture was degassed under vacuumand backfilled with argon before of anhydrous chlorobenzene was added.The solution was then heated and poured into methanol. The solid PolymerA was filtered and purified by Soxhlet extraction and dried overnight.

Polymer B Synthesis

In yet another embodiment, the polymer synthesis can be compounds5,5′″-dibromo-3,3′″-bis(2-butyloctyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiophene,(4,8-bis(5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(trimethylstannane),(4,8-bis(4-fluoro-5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(trimethylstannane),Pd2dba3 and P(o-tol)3 were added. The mixture was degassed under vacuumand backfilled with argon before of anhydrous chlorobenzene was added.The solution was then heated and poured into methanol. The solid PolymerB was filtered and purified by Soxhlet extraction and dried overnight.

Polymer C Synthesis

In yet another embodiment, the polymer synthesis can be compounds5,5′″-dibromo-3,3′″-bis(2-butyloctyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiophene,(4,8-bis(5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(trimethylstannane),Pd2dba3 and P(o-tol)3 were added. The mixture was degassed under vacuumand backfilled with argon before of anhydrous chlorobenzene was added.The solution was then heated and poured into methanol. The solid PolymerC was filtered and purified by Soxhlet extraction and dried overnight.

Polymer D Synthesis

In yet another embodiment, the polymer synthesis can be compounds5,5′″-dibromo-3,3′″-bis(2-butyloctyl)-3″,4′-difluoro-2,2′:5′,2″:5″,2′″-quaterthiophene,(4,8-bis(4-chloro-5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(trimethylstannane),Pd2dba3 and P(o-tol)3 were added. The mixture was degassed under vacuumand backfilled with argon before of anhydrous chlorobenzene was added.The solution was then heated and poured into methanol. The solid PolymerD was filtered and purified by Soxhlet extraction and dried overnight.

Anode

When used in as an organic photovoltaic device the polymer can be usedin conjunction with an anode. The anode for the organic photovoltaicdevice can be any conventionally known anode capable of operating as anorganic photovoltaic device. Examples of anodes that can be usedinclude: indium tin oxide, aluminum, silver, carbon, graphite, graphene,PEDOT:PSS, copper, metal nanowires, Zn₉₉InO_(x), Zn₉₈In₂O_(x),Zn₉₇In₃O_(x), Zn₉₅Mg₅O_(x), Zn90Mg₁₀O_(x), and Zn85Mg₁₅O_(x).

Cathode

When used in as an organic photovoltaic device the polymer can be usedin conjunction with a cathode. The cathode for the organic photovoltaicdevice can be any conventionally known cathode capable of operating asan organic photovoltaic device. Examples of cathodes that can be usedinclude: indium tin oxide, carbon, graphite, graphene, PEDOT:PSS,copper, silver, aluminum, gold, metal nanowires.

Electron Transport Layer

When used in as an organic photovoltaic device the copolymer can bedeposited onto an electron transport layer. Any commercially availableelectron transport layer can be used that is optimized for organicphotovoltaic devices. In one embodiment the electron transport layer cancomprise (AO_(x))_(y)BO_((1-y)). In this embodiment, (AO_(x))_(y) andBO_((1-y)) are metal oxides. A and B can be different metals selected toachieve ideal electron transport layers. In one embodiment A can bealuminum, indium, zinc, tin, copper, nickel, cobalt, iron, ruthenium,rhodium, osmium, tungsten, magnesium, indium, vanadium, titanium andmolybdenum.

In one embodiment B can be aluminum, indium, zinc, tin, copper, nickel,cobalt, iron, ruthenium, rhodium, osmium, tungsten, vanadium, titaniumand molybdenum.

Examples of (AO_(x))_(y)BO_((1-y)) include: (SnO_(x))_(y)ZnO_((1-y)),(AlO_(x))_(y)ZnO_((1-y)), (AlO_(x))_(y)InO_(z(1-y)),(AlO_(x))_(y)SnO_(z(1-y)), (AlO_(x))_(y)CuO_(z(1-y)),(AlO_(x))_(y)WO_(z(1-y)), (InO_(x))_(y)ZnO_((1-y)),(InO_(x))_(y)SnO_(z(1-y)), (InO_(x))_(y)NiO_(z(1-y)),(ZnO_(x))_(y)CuO_(z(1-y)), (ZnO_(x))_(y)NiO_(z(1-y)),(ZnO_(x))_(y)FeO_(z(1-y)), (WO_(x))_(y)VO_(z(1-y)),(WO_(x))_(y)TiO_(z(1-y)), and (WO_(x))_(y)MoO_(z(1-y)).

In an alternate embodiment, various fullerene dopants can be combinedwith (AO_(x))_(y)BO_((1-y)) to make an electron transport layer for theorganic photovoltaic device. Examples of fullerene dopants that can becombined include

and [6,6]-phenyl-C₆₀-butyric-N-2-trimethylammonium ethyl ester iodide.

In the embodiment of

R′ can be selected from either N, O, S, C, or B. In other embodiment R″can be alkyl chains or substituted alkyl chains. Examples ofsubstitutions for the substituted alkyl chains include halogens, N, Br,O, Si, or S. In one example R″ can be selected from

Other examples of fullerene dopants that can be used include:[6,6]-phenyl-C₆₀-butyric-N-(2-aminoethyl)acetamide,[6,6]-phenyl-C₆₀-butyric-N-triethyleneglycol ester and[6,6]-phenyl-C₆₀-butyric-N-2-dimethylaminoethyl ester.

Organic Photovoltaic Device Fabrication

Zinc/tin oxide (ZTO):phenyl-C60-butyric-N-(2-hydroxyethyl)acetamide(PCBNOH) sol-gel solution was prepared by dissolving zinc acetatedihydrate or tin(II) acetate in 2-methoxyethanol and ethanolamine.Specifically, the ZTO:PCBNOH sol-gel electron transport layer solutionwas prepared by mixing Zn(OAc)₂ (3.98 g), Sn(OAc)₂ (398 mg) and PCBNOH(20.0 mg) in 2-methoxyethanol (54 mL) with ethanolamine (996 μL).Solutions were then further diluted to 65 vol % by adding more2-methoxyethanol and stirred for at least an hour before spin castingonto indium tin oxide substrate to form the electron transport layer.

In alternate embodiments, the formation of ZTO([6,6]-phenyl-C₆₀-butyric-N-2-trimethylammonium ethyl ester iodide(PCBNMI) can be used as well. One method of forming PCBNMI can be taking[6,6]-phenyl-C60-butyric-N-2-dimethylaminoethyl ester (0.05 g, 0.052mmol) and dissolved it in dry THF (2 mL) under argon. Iodomethane (1.5mL) was added in one portion and the vessel was sealed. The solution isthen heated to 60° C. for 18 hours. The solution was cooled and openedto allow the liquids to evaporate. The solid residue was suspended inmethanol, diluted with acetone, and centrifuged. This process wasrepeated to produce [6,6]-phenyl-C60-butyric-N-2-trimethylammonium ethylester iodide as a metallic green powder (0.05 g, ˜99% yield).

The polymer and the acceptor, EH-IDTBR, in a ratio of 1:2 were dissolvedin toluene at the concentration of 27 mg/mL to obtain the photoactivelayer solution. The solution was stirred and heated at 80° C. overnightin a nitrogen filled glove box. The next day from about 0-0.5% vol % of1,8-diiodooctane (DIO) was added before spin-coating of the photoactivelayer.

Indium tin oxide patterned glass substrates were cleaned by successiveultra-sonications in acetone and isopropanol. Each 15 min step wasrepeated twice, and the freshly cleaned substrates were left to dryovernight at 60° C. Preceding fabrication, the substrates were furthercleaned for 1.5 min in a UV-ozone chamber and the electron transportlayer was immediately spin coated on top.

Sol-gel electron transport layer solution was filtered directly onto theindium tin oxide with a 0.25 μm poly(vinylidene fluoride) filter andspin cast at 4000 rpm for 40 s. Films were then annealed at 170° C. for15 min, and directly transferred into a nitrogen filled glove box.

The photoactive layer was deposited on the electron transport layer viaspin coating at 1600-4000 rpm for 40 s with the solution and thesubstrate being preheated at 80° C. and directly transferred into aglass petri dish for to be dried.

After drying, the substrates were loaded into the vacuum evaporatorwhere MoO₃ (hole transport layer) and Ag (anode) were sequentiallydeposited by thermal evaporation. Deposition occurred at a pressure of<4×10⁻⁶ torr. MoO₃ and Ag had thicknesses of 5.0 nm and 120 nm,respectively. Samples were then encapsulated with glass using an epoxybinder and treated with UV light for 3 min.

Photovoltaic Device Performance

TABLE 1 Polymer V_(oc) (V) Jsc (mA/cm²) FF (%) PCE (%) A 1.03V 15.0 60%9.0% B 0.99V 14.8 54% 7.9% C 1.02V 14.9 65% 9.9% D 1.14V 8.0 49% 4.5%

These results indicate higher quality films with a reduction incrystallite formation are beneficial to improve the overall powerconversion efficiency. Jsc (mA/cm²) Short-circuit current density (Jsc)is the current density that flows out of the solar cell at zero bias.V_(oc) (V) Open-circuit voltage (V_(oc)) is the voltage for which thecurrent in the external circuit is zero. Fill factor percentage (FF %)is the ratio of the maximum power point divided by the open circuitvoltage and the short circuit current. PCE (%) The power conversionefficiency (PCE) of a photovoltaic cell is the percentage of the solarenergy shining on a photovoltaic device that is converted into usableelectricity.

FIG. 12 depicts the current density over voltage for the Polymer A.

In closing, it should be noted that the discussion of any reference isnot an admission that it is prior art to the present invention,especially any reference that may have a publication date after thepriority date of this application. At the same time, each and everyclaim below is hereby incorporated into this detailed description orspecification as an additional embodiment of the present invention.

Although the systems and processes described herein have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made without departing from the spirit and scopeof the invention as defined by the following claims. Those skilled inthe art may be able to study the preferred embodiments and identifyother ways to practice the invention that are not exactly as describedherein. It is the intent of the inventors that variations andequivalents of the invention are within the scope of the claims whilethe description, abstract and drawings are not to be used to limit thescope of the invention. The invention is specifically intended to be asbroad as the claims below and their equivalents.

1. A method comprising: combining

tris(dibenzylideneacetone)dipalladium(0), and tris(o-tolyl)phosphine toproduce

and combining

with n-bromosuccinimide and anhydrous tetrahydrofuran to produce thecomonomer

wherein X₁ and X₂ are independently selected from the group consistingof: F, Cl, H, and combinations thereof; and wherein R₁ is independentlyselected from unsubstituted or substituted branched alkyls with 1 to 60carbon atoms and unsubstituted or substituted linear alkyls with 1 to 60carbon atoms.
 2. A photovoltaic device comprising the comonomer of claim1 as a photovoltaic material.
 3. An electronic device comprising thecomonomer of claim 1 as an active layer material.
 4. A methodcomprising: combining

tris(dibenzylideneacetone)dipalladium(0), and tris(o-tolyl)phosphine toproduce

and combining

with n-bromosuccinimide and anhydrous tetrahydrofuran to produce thecomonomer

wherein R₁ is independently selected from unsubstituted or substitutedbranched alkyls with 1 to 60 carbon atoms and unsubstituted orsubstituted linear alkyls with 1 to 60 carbon atoms.